Torque limiting device



July 3 A. B. DE SAl .ARDl

TORQUE LIMITING DEVICE Filed Oct. 8, 1956 2 Sheets-Sheet l Mali . 55 INVENTOR y 3 A. B. DE SALARDI 2,164,870

TORQUE LIMITING DEVICE Filed Oct 8, 1936 2 Sheets-Sheet 2 M FigJZ [518. FigIIQ 0j9 67 Patented July 4, I939 NITED STATES PATENT OFFICE TORQUE LIMITING DEVICE Application October 8,

4 Claims.

My invention relates to devices connecting a driving and 'a driven member of a mechanical power transmission having the purpose to transmit torque limiting it to an allowed maximum.

Heretofore parts of a mechanical power transmitting system had to be largely over-dimensioned to take care of the dynamic stresses due to shocks and excess loads which occur as unavoidable incidents to almost all mechanical operation, and even these over-dimensioned parts were often broken, or excessively worn due to such shocks and excess loads, necessitating the suspension of operation and costly repairs.

To avoid such costly repairs, easier exchangeable low-cost frangible members like bolts and pins weakened by grooves, etc., were introduced to protect the more expensive parts. These reduced the cost of the repair in each instance somewhat, but making the breakage more frequent, instead of eliminating it, the method provided little relief.

Another attempt of limiting the torque by slip couplings known today is practicable only in special cases, where such expensive, heavy, cumbersome and voluminous addition like a known slip coupling is allowable. Besides slip couplings of conventional .design wear out relatively quickly, their parts being subjected to heavy sliding friction.

The present invention does away with the above draw-backs as it limits the transmitted torque to a pre-determined maximum between the driving and the driven members obviating their breakage. One object of my invention is thus to limit the torque transmitted between the rotating members of a mechanical power transmission to a pre-determined allowable maximum by automatically disengaging the members, when the torque becomes greater than the allowed safe maximum, and re-engaging them, when the torque becomes equal to or less than such safe maximum. Another object is to eliminate the danger of breakage or excessive wear of the power transmitting parts. Still another object is to make possible the employment of comparatively lighter parts in a mechanical power transmission and of the driven machinery by maintaining safety against breaking. Andanother object is to reduce the space needed for such mechanical power transmission.

These and other objects will be clearly eviden from the following description and attached drawings in which:

Fig. .1 shows a fragment of a spur gear and a shaft as exemplary two members of a mechanical 1936, Serial No. 104,656

power transmission between which torque is to be transmitted. The spur gear is shown partly in elevational view but substantially in a radial section, rotatably mounted on a shaft, shown in radial section. These two, driven and driving 1 members, are connected by locking elements comprising antifrictional pressure bearing parts, such as balls.

Fig, 2 is a fragmentary axial sectionon the line 11-11 of Fig. 1.

Fig. 3 is a partial axial section of the same first group of the invented device as illustrated by Fig. 1 with the diiference that the employed antifrictional locking members are rollers.

Fig. 4 is a diagrammatical axial sectional view of another embodiment belonging to the first group in which antifrictional locking members are used between driving and driven parts which are discs mounted adjacent to each other on the co-axial shafts.

Fig. 5 is a iragmental view chiefly in radial section of a spur gear mounted on a shaft and connected to it with an embodiment of the second group of the invented device comprising wedgelike looking elements.

Fig. 66 is a fragmental axial sectional view taken on line VI-VI of Fig. 5.

Fig. 7 is a fragmental axial sectional view of substantially the same embodiment as shown in Figs. 5 and 6 except that instead of the individual adjacent wedge-like locking members these are united into locking bars.

Fig. 8 is a fragmental view substantially in radial section of an embodiment belonging to the first group of the invented device employing antifrictional pressure bearing locking elements between the driving and driven parts, latter being provided with guiding means for leading such locking elements.

Fig. 9 is a fragmental axial section on the line IXIX of Fig. 8.

Fig. 10 is a plan view of a key-like insert in the shaft, the former provided with seats for the balls and with a bore to admit lubricant.

Fig. 11 is a fragmental axial section of substantially the sameembodiment as shown in Figs. 8 and 9, except that instead of balls one or more rollers are employed as locking elements between the driving and driven members.

Fig. 12 is the plan view of a key-like insert in the shaft provided with a suitable seat for a roller and with a bore to admit a lubricant.

Fig. 13 is a fragmental view chiefly in radial section of an embodiment belonging tov the third group of the invented device in which the locking elements and co-operating parts between driving and driven members are enclosed in one or more casings attached to the driving and driven members respectively.

Fig. 14 is a fragmental axial section on. the line XIV-XIV of Fig. 13.

Fig. 15 is a fragmental axial section of substantially the same embodiment which is shown in Figs. 13 and 14, except that instead of balls one or more rollers are used as antiirictional pressure bearing locking elements.

Fig. 16 is a perspectiveview of an exemplary embodiment of the casing holtfing the locking elements and the cooperating parts.

Fig. l? shows a fractional view substantially in radial section of an embodiment belonging to the third group as illustrated by the Figs. 13, i l, and 15 with the difierence that the casings harboring the locking elements are solid prismatic blocks that are provided with cylindrical bores which the cylindrical guides of the locking elements are reciprocably mounted, subjected to the pressure of the cooperating springs.

Fig. 18 is a fragmental axial sectional view on the line XVIfi-JXVHX of Fig. 17.

Fig. 19 is a sectional view taken on line of Fig. 18.

2G is a iragrnental view substantially of a radial section of an embodiment belonging to the third group of the invented device in. which wedge-like locking members are employed groupin the casings, attached to the driving or driven members, respectively.

21 is a fragmental axial sectional view on the iine 2n; of Fig, 20.

Fig. 22 is a fragmental axial sectional view of another embodiment of the first group in which antiirictional pressure bearing locking members, such as balls, are arranged in boresof a hub of a gear, such balls cooperating, under pressure of springs with suitable seats provided in lreylilre inserts of the shaft upon which the gear is rotat ably mounted.

Fig. 23 is a radial sectional view taken on the line a ...Q"Il of Fig. 22., I Fig. 24 is a iragrnental axial sectional view of an embodiment of the third group of the invented device in which two powertransrnitting, rotatably co=-ai:ially mounted bodiesone being the driving, other the driven member eachhave one ringiilre body, securely attached to it, the inner ringlilre body being the casing of the antifrictional pressure bearing locking elements and the outer ringlike body carrying the seats cooperating said locking elements.

Fig. 25 is the partial radial sectional view on the line mV-QQ LV of Fig. 24.

Fig. 26 shows substantially the same embodimerit as shown in Figs. 24 and 25 with the difierence that of the two rings interposed between the driving and driven rotatable members the inner one (keyed to the shaft) is provided with seats for the locking elements, and the outer ring with bores to accommodate the locking elements, the compressing springs and. their tension regulating means.

Fig. 27 is a partial radial sectional view on the line XXVH-XXVII of Fig. 26.

Referring closer to the drawings by the characters of reference, Figs. 1 and 2 show an examplary embodiment of the first group within the scope of the invention, in which group the locking elements, having a body generated by revolution of a plan figure around an axis, specifically shown to be balls, cooperate with the drivamo s /o jacent to the shaft 2 are apertures or recesses 3 with openings toward shaft 2, in which recesses the balls i are movably accommodated. The diameters of the balls 3 are somewhat smaller than the width of the apertures 35 to allow the movement of the balls within said apertures.

Cups ii-accommodating one end portion of helical spring t-are mounted slideably in aper-' tures Each aperture 3 shelters a number of sets of balls 1, cups 5, and compressing-springs it, this number of sets shown to be three as an example.

Spacers serve to adjust the position of cups 5 in radial direction and with it the pressure of springs with which these urge the balls 1 to occupy suitable seats 8 formed in the surface of shaft 2 at such locations that are corresponding to those of the balls l. The shape of the seats 8 shown is a spherical cap corresponding to the diameter of balls G.

Spacers U are provided preferably at one end with a wedge-like portion facilitating their insertion, and at their other end with a head 9 for convenient extraction. For the sake of simplicity only one such spacer l is shown in each aperture 3. The adjustment of the radial position of cups ti and with it the pressure of the springs [5 is effected by inserting thicker or thinner spacers ll.

in the exemplary embodiment three apertures 3 are shown, spaced at 120degrees from each other, each recess accommodating three balls l. it will be understood, however, also in cases of any other embodiments shown or conceivable in the scope of the invention, that any number of apertures, locking members, seats and springs can be employed in equal angular spacing around the axis to cooperate between driving and driven members, depending upon their dimensions, the tordue to be transmitted and on the material of the cooperating parts.

The recesses 3 in spur gear l and the seats 3 in the shaft are arranged in equal angular spacing so that in the position in which one aperture faces one row of seats, every other aperture does this with respect to another row of seats.

Gear l is shown to be provided with a counterbore on each of its faces in which discs ill and it are fitted and held firmly by the screws l2 to the gear [1, the latter having suitable bores l3, serving to admit the screws.

Discs iii and it have the necessary central bores for sliding, together with gear l, on the shaft Cooperating with the shaft 2, the discs it and 6!] may have grooves it or other suitable means to retain lubricant in the apertures 3 that are dust-proofingly closed in axial direction by the discs it and M.

Screws 02 are shown to have countersunk heads accommodated in disc lb and screwed into the tapped holes of disc M, which has suitable recesses for heads 9 of spacers l. Screws l2 are provided with suitable locking means, such as a riveted-down tip, shown.

It is evident that any other type of screw, bolt, rivet or approved attachment and locking means can be used to hold the discs securely to the gear.

In Fig. 1 a fragment of the disc M is shown in elevational view the rest being broken away. Gear I is rotatably mounted on a suitable seat of shaft 2 and is prevented to shift axially by suitable means, such as shoulder I5 of shaft 2 and washers I6 held against disc II by nut I1, which is mounted on the threaded portion of shaft 2 and locked by adequate means, such as set-screws I8, to said shaft 2.

Ducts I9 in shaft 2 branching out from a lubrication fitting (not shown) reach all recesses 3 and serve to convey to them the lubricating material.

The operation of the device is described as follows:

Balls 4, urged by springs 6 into seats 8, look gear I to the shaft 2 so that gear I will turn together with shaft 2 as one unit when torque is transmitted from the shaft, or vice versa, until the magnitude of the torque does not exceed the limit at which the radial component of the torque, acting against the pressure of springs 6, equals that pressure in addition to the friction, counteractingthe movement of the balls relative to their seats 8.

In the event that the transmitted torque for any reason whatsoever, rises to such a magnitude that its radialcomponent overcomes the spring pressure and the friction, the balls 4 will be thrown out of seats 8 radially against the spring pressure, and the gear I will idle on shaft 2. During such idling the balls will oscillate radially within recesses 3, jumping into and out of seats 8 until the cause of the excessive torque is removed.

When the torque decreases to or below the permitted maximum-determined in a given device by the pressure of the springs and the frictionthen the pressure of the springs 6 (properly adjusted) becomes greater than the radial component of the torque acting against them, and the pressure'of springs 6 will cause the balls 4 to retain the seats 8 reestablishing fixed relative positions of gear I in respect to shaft 2.

The locking of the driving and the driven members to each other is entirely automatic and is caused .by the variation of the value of the torque, thus eliminating the danger of 'a possible break or excessive wear due to sudden overloads and shocks, incident to almost every utilization of mechanical power.

By making the locking members and cooperating surfaces accurately machined, suitably hard and providing for adequate lubricationand sealing, the periodical disengagement of the locking members from the seats and their engagement with them, respectively, will not injure any of the parts and the device will outlive Practically the rest ofthe machinery.

In dimensioning and adjusting, respectively, the springs ,6 allowance has to be made for the centrifugal forces acting radially, which, however, will aifect the dimensions only when comparatively high speeds and locking elements of substantial weight are employed.

Fig. 3 is a fragmental axial section of an em-v bodiment which is substantially the same as shown in Figs. 1 and 2 with the exception that instead of three row of balls, three rollers 20 are used as locking elements between the gear I and shaft 2. A radial cross section of Fig. 3 would show the same picture as Fig. 1; hence it is omitted to avoid repetition. The like parts are identified by like characters, for the descfription of which reference is made to that of Figs. 1 and 2. Differing parts are cups 2|, each accommodating one roller and two springs in shaft 2 and the seats 22 which have a cylindrical portion to fit the rollers 28.

The operation of this embodiment is similar to that of the embodiment shown in Figs. 1 and 2 inasmuch as the radial components of the excessive torque will throw out the rollers 20 from .seats 22 radially against the pressure of the springs 6.

Fig. *4 shows a third embodiment of the first group having as locking members bodies of a shape generated by revolution of a plane figure around an axis, shown to be balls. The driving anddriven members are shown to be co-axial discs 23 and 24, for the sake of simplicity shown to be of one integral piece with their shafts, r0- tatably mounted in bearings 25 and 26.

The peripheral portion of disc 23 has apertures 21 in which balls 4 and springs 6 are accommodated. The springs 8 urge the balls 4 to occupy the seats 8 in disc 24, located correspondingly to apertures 21. Both are arranged in equal. angular spacing in the discs 23 and 24 respectively.

The apertures 21 have a tapped hole to suit the adjusting screws 28 the end of which is servmeans, e. g., the whole device can be inclosed in a lubricant containing casing 30 (shown broken away).

Washers 3| between the discs 23, 24, and bearings 25, 28, respectively, serve to restrain axial movement of the discs, which purpose can be attained by other known means such as thrust bearings, collars, etc.

The operation of this embodiment is similar to that of the previous ones except that'the radial component of the excessive torque will eject the Us 4 from their seats 8 in axial direction against the pressure of springs B.

Figs. 5 and 6 illustrate an embodiment of the second group of the device within the scope of my invention, in which group the locking elements between the driving and driven members have a shape bounded by at least one plane surface, which, cooperating with a guide, prevent the turning of the locking element having one end portion wedge-shaped preferably with rounded edge. In the embodiments of the second group, shown herein, the locking elements are illustrated to be substanti lly cuboids topped by a wedge-shaped end porti the edge of which is being rounded.

For sake of simplicity the driving and driven members, respectively, are shown to be spur gear 32 and the shaft 33, the former being mounted .rotatably on the latter.

In the central portion of the spur gear 32 are recesses or apertures 34 with openings toward the shaft 33, in which apertures the prismatic bodies 35 are reciprocably mounted, guided by the walls of the apertures 34. v

.- "One end portion of the locking elements 35 slidably accommodated in the apertures 36, the spring pressure being adjustable by'the insertion of one or more spacers l, provided with heads ii.

Seated fittingly in counterbores in both faces of gear 3!, discs 38 and 39 cover the end portions of the seat-grooves 36, which may be longer in axial direction than is the width of the gear 32, and seal dustproofingly the apertures 3d.

In their central bore the discs are provided with several lubricant retaining grooves M cooperating with shaft 33. Disc is provided with suitable recesses to accommodate heads $3 of spacers 1.

The discs 38 and 39 are held to the gear 32 by suitable means such as screws lb which traverse the gear 32 in suitable bores and are sufficiently riveted down or otherwise deformed at their ends after the assembly to prevent accidental loosening.

Gear 32 is restrained axially on shaft 33 by suitable means such as the shoulder 55 in one direction and in the other by washer iii, nut ll' mounted upon a threaded portion of shaft 33- the nut it being provided with locking means such as set-screws l8.

Ducts i9 serve to convey lubricating material from a known fitting (not shown) into the aperturest l, while grooves ll in the surfaces of the locking members 35 admit the lubricant further into the apertures M.

Fig. 6 shows three individual locking elements operating adjacently in an aperture 36. A suitable number of apertures can be arranged holding the described operating members, which apertures-similarly to as many seat-grooves in the shaft 33are arranged in equal angular spacing.

The torque being transmitted between the gear 32 and shaft 33, by contacting sides of locking elements 35 and seat-grooves and the reactionbeing perpendicular to the surfaces, it will have a radial component which tends to eject the locking bodies 35 from the grooves 33 against the pressure of the springs As long the pressure of the springs in addition to the friction between the locking elements, their seats and guiding parts is greater than the radial component of the transmitted torque, the locking elements retail their seats in the grooves 33 and the gear 32 turns as one body with shaft 33.

In the event that the transmitted torque, for any reason whatsoever, rises to such a magnitude that its radial component overcomes the spring pressure and the friction, the; locking elements 35 will be ejected 'from the seats 36 radially against the spring pressure, and the gear 32 will idle on shaft 33 or the shaft 33 will idle in gear 32 according to which part is the driven one. During the idling the locking elements will oscillate radially within the apertures 3d, jumping into and out from the seats as long as the excessive torque is prevailing.

When the torque becomes equal to or less than the permitted maximum then the pressure of the springs, dimensioned or adjusted accordingly, will .exceed the radial component of the torque and cause the locking members 35 to retain the seats 36 re-establishing fixed relative positions of the gear 32 with respect to the shaft 33.

Fig. 7 shows substantially the same embodiment of the second group, except that instead of the several individual locking elements in each recess there is one looking bar 32 reciprocatingly mounted in each aperture 33 of the gear 32. Ducts'43 admit the lubricant through the locking bar 42 into the outer space of the'recesses 34.

A radial section of this embodiment will give a picture similar to Fig. 5.

Fig. 8, 9 and 10 show a fourth embodiment of the first group. The torque transmitting member M1 is mounted rotatably on shaft 65, constituting the driving and driven members of a power transmission.

Member M has apertures Alt open toward the shaft 53, each aperture accommodating one or more reciprocably mounted guides ll having suitably fo-rmed deepenings for balls 41. Springs 6 in nests 13 pressing upon guides 67] urge balls 6 to enter the seats 8 formed in the surface of keylike inserts d9 accommodated in suitable keyways in shaft 65.

Discs Eiil and 5B, seated in counter-bores on both faces of member i l and having suitable bores to cooperate with the shaft 65, are attached by known means such as screws i2 to the member Ml.

Discs 5t and iii dust-proofingly seal the apertures mi in axial direction. Discs 5i has suitable recesses to accommodate heads 3 of spacers 7 serving as adjustment means for regulating the pressure of the springs 6 upon balls i and with it the transmissible maximum torque.

Axial restraining of the member M with respect to shaft 35 is attained by suitable means such as shoulder 05 in one direction, and in the other by the washer l6, and nut ll mounted on the threaded portion of shaft 35, said nut ll being locked to the shaft 35 by suitable means such as set-screw it.

The arrangement of the ball seats ii in easily exchangeable inserts 39 has the purpose to make a renewal inexpensive.

Ducts l9 convey the lubricant from a fitting (not shown) to the balls l. Guides ii are provided with grooves ll to admit the lubricant into the outer portion of apertures 16. One or more apertures may be arranged in member (i i in which latter case they are located preferably in equal angular spacing. The same holds true of the key-like inserts 19.

Aperture it is shown to accommodate two sets of balls, guides and springs but they may accommodate any suitable number of them.

Fig. 10 is the plan view of an insert lii provided with two ball seats ii and a lubricating duct. The operation of this embodiment is similar to that shown in Figs. 1 and 2 to the description of which I refer.

Figs. 11 and 12 show a fifth embodiment of the first group which differs from that illustrated in Figs. 8 and 9 only that between the driven and driving members 56 and 55, respectively, the rollers 52 are employed, instead of balls, as locking members.

Throughout the description the member designated as driving is that upon which the driving power acts, and the driven is that connected with the load or resistance.

The rollers 52 are mounted oscillatably in apertures d6 of member 66 and are urged by springs 6, positioned in nest it, pressing upon guide 33 which is suitably recessed to accommodate partially the roller 52. The latter is urged by the pressure of the springs to occupy seat 541 in the key-like insert 55 accommodated in suitable keyways in the shaft 35.

Discs 50 and 50, spacers l, attachment screws 02, lubricant retaining grooves i l, lubrication ducts l9, grooves ll, retaining washers it, shoulder it serve in the-same wayas described in the previous figures.

Nut 56 on the threaded portion of shaft prevents axial motion of the unit on the shaft 45.

Set-screw 51 is shown as locking means which is inserted in axial direction in nut 56 and shaft 45.

Fig. 11 is a fragmental axial sectional view; a radial sectional view of the same embodiment would look exactly like Fig. 8.

Fig. 12 is a plan view of a key-like insert showing the seat 54 and a lubrication bore.

While in the embodiments shown in Figs. 1 to I 12 each part is to be handled and inserted separately, Figs. 13 to 27 illustrate a third group of embodiments in which the locking elements and cooperating parts are accommodated in cages, carriers, or rings forminga unit which is easily insertable between the driving and the driven members. This facilitates the assembling and disassembling.

Fig. 13 is a fragmental radial sectional view and Fig. 14 a fragmental axial sectional view of the first embodiment of the third group.

This embodiment is created substantially by employing all the parts ofthe embodiment shown in Figs. 8 and 9 and placing the locking elements and cooperating parts'in carriers 58 which are shaped as casings fitting the suitably dimensioned apertures 46 in the torque transmitting member 44.

Nut 56 and locking set screw 51 are similar to those of Fig. 11.

Fig. 15 is another embodiment of the third group developed by using the parts of Fig. 11, placing them in suitable casing 58 accommodated in the apertures 46 of the torque transmitting member 44. Q

A radial section of the embodiment shown in Fig. 15 would be like Fig. 13.

For description of the parts shown .in Figs. 13,

14, 15, I refer to such given for those designated by identical characters in the Figs. 8&0 12.

Fig. 16 shows the detached, casing-shaped carrier 58 in axometric projection. s,

Figs. 17, 18, 19, show a third embodiment of the third group of the device. Fig. 1'7 is a fragmental' radial sectional view of the device a portion of it being an elevational view. Fig. 18 is a fragmental axial section on line XVIII--XVIII of Fig. 17 and Fig. 19 is a sectional view on the line XIX-X[X-of Fig. 18.

. This embodiment is similar to that illustrated in Figs. 13 and 14, except, that the carrier of the locking elements is a solid block 59 in which bores 68 are arranged to receive cylindrical, plunger-like guides 5| holding the antifrictional locking elements, such as balls 4 that are urged by the springs 6 to occupy the suitable seats 8 in the key like inserts 62 seated in suitable key-ways in shaft 53.

This shaft 63 is one of the driven respectively driving members while the member 64, rotatably arranged upon it, is the other one which is provided with the apertures 45 accommodating the blocks 59.

Springs 6 are also seated in cups 65 which are reciprocably mounted in the bores they are backed by spacers I the number and thickness of which are chosen to regulate the spring pressure upon guides BI and balls 4.

Disc 66 seated in a counter-bore in one face Disc 58 mounted adjacent the other face of the rototable body 64 is split into two halves which are provided with a tongue and groove connection with each other so that they are radially insertable into grooves 69 of shaft 63.

Discs 86 and 68 are fastened together and to the rotatably mounted body 64, the apertures of which they seal, by suitable means such as screws I2 shown that pass through adequate bores through the member 64.

Ducts I9 and grooves 4| serve to convey the lubricant into the recesses 46 and bores 68, re-

spectively. 7

Split disc 68 has suitable recesses for heads 8 of spacers 'I. I

The operation of this embodiment is substantially the same as that of the embodiments shown in Figs. 1 and 2. When excessive torque acts upon the device its radial component ejects the balls 4 from the seats 8 against the pressure of springs 6, and the rotating body 64 will idle upon and relative to the shaft 63 taking along the discs 66 and 68 which are slidable on the shaft and in the groove 69, respectively, securing the rotating body 64 axially upo'n shaft 63.

Figs. 20 and 21 illustrate a fourth embodiment of the third group of the invented device. This embodiment was developed by placing the wedgeshaped locking elements 35, shown in the embodiment illustrated in Figs. 5 and 6, together with their springs 6 and nests 10 in the casing 58 occupying apertures 46 of the transmission member ll mounted on shaft 12.

Spacers I serve to adjust the spring pressure with which the wedge-shaped locking elements 35 are .urged against the suitably shaped seats [3 arranged in' keylike inserts '14 in the key-ways cut in the shaft 12.

Lubricating ducts I 9 starting from lubricating fitting '15 lead to suitably located holes of key-like iinserts l4 and to grooves 48, in the locking ele- -ments 35.

Discs 16 and 11' are accommodated in suitable counter-bores on both faces of member II to which they are attached by suitable means such as screws l2.

Member H is secured in axial direction by discs 15 and Ti cooperating with shoulder 18 of shaft 123 toward the right, and collar 19 toward the left, which is secured to shaft 12 by suitable means such as set screws 80.

The ejectment of locking elements 35 from their seats 13 in key-like inserts M will automatically follow the increase of the torque between the driven and driving members it and i2 similarly to operation described for the-embodiment shown in Figs. 5 and 6.

Figs. 22 and 23 show in fragmental axial and radial sectional views, respectively, the sixth embodiment of the first group of the device,

The torque transmitting member 8| shown to be a gear with an axially protruding hub-portion is rotatably mounted upon shaft 82.

The protruding hub-portion 83 is provided with bores 84 in which balls 4, plunger-like guides and springs 6 are reciprocably arranged, retained by suitable scews 85 adjustably mounted in the threaded portion of bores 84.

By turning screws 85 the pressure of springs 6 upon guides 61 and balls 4 can be adjusted. Springs Surge balls 4 to occupy seats 8 in the key-like inserts 62, seated at equal angular spacing in shaft 82 just as the bores 84 are located around in the protruding hub-portion 83 of gear 8|. The latter is secured axially by shoulder part 81 of shaft 82 toward the right, and by collar I9 locked to the shaft 82 by the set screws 89 toward the left.

Ducts I9 and grooves 4I serve to convey lubri'= cant to contact surfaces; the set-screws (Fig- 23) serve to lock the spring adjusting screw 85.

The function of this embodiment of the in-=,

transmitting system are represented by body 88 y and shaft 89, respectively, between which coaxially arranged are rings 99 and 9|.

Ring 99 fits upon a seat of shaft 89 to which it is attached rigidly by suitable means such as keys 82.

Ring 99 has radial bores 93 in'which plungerlike guides (SI-accommodating in suitable impressions toward the periphery the balls 4 and toward the center the springs 6-are mounted reciprocably.

Spacers 94 supporting springs 6 in extensions of a smaller diameter of bores 93 serve-to regulate the spring pressure by the variation of their number and thickness.

The pressure of the springs 6 urges balls 4 to occupy the suitable seats 8 formed in the inner surface of ring 9| and arrangedjust like the bores 93-in equal angular spacing around the common axis.

Ring 9| is rigidly attached to the torque trans= mitting member 88 by suitable means such as keys 95.

Shoulder 96 of shaft 89 cooperates with one face of ring 99 preventing its shifting toward the right.

The shoulder 91 of ring 99 prevents the axial movement of ring 9i toward the right. Shoul der 98 of ring 9i restrains the torque transmitting member 88 in the same direction.

Disc 89, fitted into a suitable counter-bore of the left face of the member 88, acts also as a seal sliding with its inner bore on shaft 89 and is securedagainst axial motion toward the left by adequate means such as washer l6 retained by nut I I mounted upon the threaded portion of shaft 89 and locked to it by set-screw l8.

Disc 99 will permit the idling of ring 8| together with the member 88 upon ring 99, but will restrain it in axial direction toward the left. Idling of the member 88 and ring 9| with respect to shaft 89 and ring 99 will follow any shock increasing the torque above the permitted maximum determined by the pressure of the springs upon the balls 4.

The lubrication fitting I5, and lubrication ducts I9 and grooves 4| convey lubricant to the moving surfaces.

Figs. 26 and 27 show substantially the same embodiment as represented in Figs. 24 and 25 except that the ring-like carrier I93 of the locking elements and their cooperating parts is mounted rotatably upon the ring I95 the latter bearing the seats 8 for balls 4. The power transmitting member I92, shown broken away, is mounted upon ring I93 to which it is attached firmly by suitable means such as keys I94 (see Fig. 2'7). Ring I93 is arranged rotatably upon the concentric ring I95 which in turn is attached rigidly by suitable means, such as keys I96, to the shaft hinder/o I197, so that the power transmitting member 692 together with ring H99 may idle upon ring H95 connected to shaft Gilli.

Ring I193 is provided with bores B98 in which plungerlike guides 88 holding antifriction pressure bearing locking elements, such as balls 9, springs Li and cups 85 are accommodated in a manner that the balls 9 are urged to occupy suitable seats 9 in the ring 895 located suitably and spaced in equal angular spacing around, similarly to bores E98.

One or more spacers l cooperating with the cups 95 serve to regulate the tension of the springs 8 determining the maximum torque transmissible with a given device.

Discs 699 and M9, firmly attached to the power transmitting body I92 by suitable means, such as screws 08, restrain the body i92 in axial direction as they cooperate with the shoulder Iii of the ring H95 and the shoulder M2 of shaft I97 preventing the axial movement toward the right while the washer I8, nut il, locked by suitable means such as set screws I8 to the threaded portion of the shaft ml, restrain the rest of the device from axial movement toward the left. Ducts i9 and grooves ll distribute the lubricant.

Disc 6 i9, acting also as a seal to the lubricated parts, has adequate recesses to accommodate heads 9 of spacers ii.

The operation of the device is similar to that described for the previous embodiments. The power transmitting members 892 and i977 revolve as a unit as long as the torque, transmitted from one to the other, does not exceed an allowable ximum and they become automatically disengaged from each other when the torque becomes greater than the allowable maximum. In this, as well as in all previously shown embodiments of invention the driving and the driven members between which torque is transmitted, are mounted rotatably around the same common axis in a manner which allows only angular motion relative to each other, any relative axial motion being prevented by thrust resisting means, so'that the locking elements are not subject of thrust forces which are accidental and would make the maximum torque to be transmitted unpredeterminable and uncertain. Also lubrication is provided in each embodiment for the surfaces subject to friction and sealing means employed to retain the lubricant and to prevent the entering of dust from the outside into the device.

Having thus fully described my invention, it is clear that various changes and alterations may be made in the form and arrangement of the parts also by substitution, multiplication, etc., without departing from the spirit and scope of the invention, hence, I do not intend to be limited by the particular embodiments herein shown and described, but

What I claim is:

1. Torque limiting device comprising a driving and a driven member coaxially rotatably mounted, guide means in fixed angular relationship to one of said members, a number of locking elements cooperating therewith for radial movement between non-locking and proper locking positions, in fixed angular relationship to the other member the same number of seats located and shaped for simultaneous coaction with finite surface areas of all of said locking elements, resilient means urging the latter to occupy said seats, and thrust resisting means preventing relative axial displacement of said locking elements and seats. i

2. Torque limiting device comprising a driving and a driven member coaxially rotatabiy mount- 5 ed, guide means in ilxed angular relationship to one of said members, a number of locking ele-' ments cooperating therewith for radial movement between non-locking and proper locking positions, in fixed angular relationship to the other mem- 10 her the same number of seats located and shaped for simultaneous coaction with flnite surface areas of all of said locking elements, resilient means urging the latter to occupy said seats, ad-

justment means for said resilient means, means 15 for conveying and retaining lubricant to, respectively between. sliding surfaces, and thrust resisting means preventing relative axial displacement of said locking elements and seats.

3. Torque limiting device comprising a driving 20 and a driven member coaxially rotatably mounted, two annular bodies each of which is coaxially fixed to one of said members, oneof said annular bodies being rotatably mounted upon the other, in one of said annular bodies guide-means,

5 a number of locking elements cooperating therewith for radial movement between non-locking and proper locking positions, in the other annular body the same number of seats located and shaped for simultaneous coaction with finite surface areas of all of said locking elements, resilient means urging latter to occupy said seats, and 5 thrust resisting means preventing relative axial displacement of said locking elements and seats.

4. Torque limiting device comprising a driving and a driven member coaxially rotatably mounted, two annular bodies each of which is coaxially 10 fixed to one of said members, one of said annular bodies being rotatably mounted upon the other, in one of said annular bodies guide-means,

a number of locking elements cooperating therewith for radial movement between non-locking 5 and proper locking positions, in the other annular body the same number of seats located and e shaped for simultaneous coaction with finite surface areas of all of said locking elements, resilient means urging latter to occupy said seats, adjust- 2o ment means for said resilient means, means for conveying and retaining lubricant to, respectively between, sliding surfaces, and thrust resisting means preventing relative axial displacement of said locking elements and seats.

ALBERT BERNHARD DE SALARDL 

